1. Field of the Invention
The present invention generally relates to broaching machinery, such as the type used to progressively broach blind splines on a workpiece. More specifically, this invention relates to a dual ram rotary blind spline broaching machine having a workpiece handling system which enables the workpieces to be loaded and unloaded at a single point along the periphery of the broaching machine table, such that easier access to the machine is provided for service and set-up, the workpiece handling system to and from the broaching machine is simplified, and the overall operating envelope of the broaching machine is reduced.
2. Description of the Prior Art
"Blind spline" broaching machines are used in the machining of splines on a workpiece, such as a shaft, which cannot be passed completely over or through a broach. Blind spline broaching machines are also suitable for forming other precision features, such as sprockets, keyways, gears, cams and contours. This type of broaching is particularly advantageous in the manufacture of precision parts in terms of machining time, which can be more than ten times faster than conventional operations, such as hobbing and shaping.
Conventionally, blind spline broaching consists of the movement of a workpiece through a series of tools which progressively remove material until the desired final dimensions are achieved. Typically, a workpiece is mounted to an indexing table which indexes the workpiece to each of a number of tools held in hydraulic rams. When its respective ram is actuated, a tool performs work on a workpiece, removing a specified amount of metal from the workpiece. The table is then indexed to align the workpiece with the next tool, and the cycle is repeated until the workpiece has encountered each tool and has been brought to its final size and shape.
Alternatively, it is known to locate the tools on the indexing table while mounting the workpieces on the hydraulic rams. An advantage here is that the number of hydraulic rams required is independent of the number of broaching operations desired. For instance, six broaching tools can be located on the indexing table while two rams, each holding a workpiece, can be actuated to broach the workpiece using two of the six tools. The table can then be indexed to align the next two tools with the workpieces until each workpiece is finished. The finished workpieces are then removed from the blind broaching machine in a preferably automated manner.
Because efficiency is increased when more than one workpiece is being machined at any given time, it is generally preferable to have more than one hydraulic ram. However, to maintain the size and complexity of a blind spline broaching machine, it is also preferable to limit the number of hydraulic rams. An illustrative example of this aspect is shown by a prior art blind spline broaching machine shown in FIG. 1. FIG. 1 is an overhead view of an indexing table 112 of a blind spline broaching machine 110. The indexing table 112 has six tool stations 114 (stations 114a through 114f) located along its periphery, along with two receptacles, referred to as "nests" 116a and 116b, for loading and unloading workpieces from the indexing table 112. Two hydraulic rams 118 are located above the indexing table 112 where indicated. The hydraulic rams 118 are diametrically opposite each other, and define two separate paths which the workpieces can take through the blind spline broaching machine 110.
For example, workpieces can pass through the blind spline broaching machine 110 by entering at a first loading station 120 and exiting at a first unloading station 122. Correspondingly, a second loading station 124 is located diametrically opposite the first loading station 120, at which other workpieces can enter the blind spline broaching machine 110. This second group of workpieces will exit the blind spline broaching machine 110 at a second unloading station 126, which is diametrically opposite the first unloading station 122. During a machining cycle, workpieces are loaded into the second nest 116b each time the second nest 116b is indexed to one of the load stations 120 and 124. Concurrently, two workpieces are held by each hydraulic ram 118 and, with each movement of the indexing table 112, the workpieces will be driven down to encounter one of the tools 114 on the indexing table 112. Once a workpiece has been broached in the last operation by the last tool 114f, the indexing table 112 is again indexed to permit the workpiece to be dropped into the first nest 116a. The subsequent indexing of the indexing table 112 will carry the machined workpiece toward one of the unload stations 122 and 126 while bringing the new workpiece into alignment with the hydraulic ram 118. The new workpiece will then be automatically secured to the hydraulic ram 118 and, with the next movement of the indexing table 112, will be machined by the successive tools 114a through 114f, starting with the tool station 114a and continuing to completion at the tool station 114f.
From the above discussion, it can be readily appreciated that the prior art blind spline broaching machines require two separate loading stations and two separate unloading stations, which must be spaced circumferentially around the blind spline broaching machine indexing table. As a result, the loading and unloading stations occupy a large portion of the circumferential space around the blind spline broaching machine, making access to the tools difficult for maintenance and repair. Further complicating the structure of the blind spline broaching machine is the requirement to have two completely separate conveyor systems to deliver and take away workpieces. As a result of the placement of the loading stations 120 and 124 and the unloading stations 122 and 126, two diametrically opposed delivery conveyors and two diametrically opposed return conveyors are required, which further obstruct access to the internal components of the blind spline broaching machine. Finally, the floor space required to accommodate the blind spline broaching machine is significantly increased due to the large amount of room required to accommodate two separate delivery and return conveyor systems. One way to greatly reduce the structure of the blind spline broaching machine would be to eliminate the need for two separate conveyor systems, while still retaining the capability to machine more than one workpiece during a given cycle.
Accordingly, what is needed is a blind spline broaching machine which incorporates workpiece handling equipment that enables the through-path of the workpieces to be altered, such that workpieces can be loaded and unloaded at a single loading/unloading station, so as to necessitate only a single delivery and return conveyor system.